An alkylation process, which is disclosed in U.S. Patent Application Publication 2006/0131209 (“the '209 publication”), involves contacting isoparaffins, preferably isopentane, with olefins, preferably ethylene, in the presence of an ionic liquid catalyst to produce gasoline blending components. The contents of the '209 publication are incorporated by reference herein in its entirety.
An ionic liquid catalyst distinguishes this novel alkylation process from conventional processes that convert light paraffins and light olefins to more lucrative products such as the alkylation of isoparaffins with olefins and the polymerization of olefins. For example, two of the more extensively used processes to alkylate isobutane with C3-C5 olefins to make gasoline cuts with high octane numbers use sulfuric acid (H2SO4) and hydrofluoric acid (HF) catalysts.
Ionic liquid catalysts specifically useful in the alkylation process described in the '209 publication are disclosed in U.S. Patent Application Publication 2006/0135839 (“the '839 publication”), which is also incorporated by reference in its entirety herein. Such catalysts include a chloroaluminate ionic liquid catalyst comprising a hydrocarbyl substituted pyridinium halide and aluminum trichloride or a hydrocarbyl substituted imidazolium halide and aluminum trichloride. Such catalysts further include chloroaluminate ionic liquid catalysts comprising an alkyl substituted pyridinium halide and aluminum trichloride or an alkyl substituted imidazolium halide and aluminum trichloride. Preferred chloroaluminate ionic liquid catalysts include 1-butyl-4-methyl-pyridinium chloroaluminate (BMP), 1-butyl-pyridinium chloroaluminate (BP), 1-butyl-3-methyl-imidazolium chloroaluminate (BMIM) and 1-H-pyridinium chloroaluminate (HP).
However, ionic liquid catalysts have unique properties making it necessary to further develop and modify the ionic liquid catalyzed alkylation process in order to achieve superior gasoline blending component products, improved process operability and reliability, reduced operating costs, etc.
There is a need for an effective and efficient process for removing ionic liquid from the hydrocarbon phase after ionic liquid catalyzed alkylation. In general, the process should be simple and efficient enough to be used to separate any ionic liquid, not just an ionic liquid catalyst, from hydrocarbons where the density of the hydrocarbons is less than the density of the ionic liquid.